# std::log10, std::log10f, std::log10l

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< cpp‎ | numeric‎ | math

Defined in header `<cmath>` |  |
| (1) |
float log10 ( float num ); double log10 ( double num ); long double log10 ( long double num ); |  | (until C++23)
/*floating-point-type*/ log10 ( /*floating-point-type*/ num ); |  | (since C++23) (constexpr since C++26)
float log10f( float num ); | (2) | (since C++11) (constexpr since C++26)
long double log10l( long double num ); | (3) | (since C++11) (constexpr since C++26)
SIMD overload (since C++26) |  |
Defined in header `<simd>` |  |
template< /*math-floating-point*/ V > constexpr /*deduced-simd-t*/<V> log10 ( const V& v_num ); | (S) | (since C++26)
Additional overloads (since C++11) |  |
Defined in header `<cmath>` |  |
template< class Integer > double log10 ( Integer num ); | (A) | (constexpr since C++26)

1-3) Computes the common (base-10) logarithm of num. The library provides overloads of `std::log10` for all cv-unqualified floating-point types as the type of the parameter.(since C++23)

S) The SIMD overload performs an element-wise `std::log10` on v_num. (See `math-floating-point` and `deduced-simd-t` for their definitions.) | (since C++26)

A) Additional overloads are provided for all integer types, which are treated as double. | (since C++11)

### Parameters

num | - | floating-point or integer value

### Return value

If no errors occur, the common (base-10) logarithm of num (log10(num) or lg(num)) is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

If a pole error occurs, -HUGE_VAL, `-HUGE_VALF`, or `-HUGE_VALL` is returned.

### Error handling

Errors are reported as specified in math_errhandling.

Domain error occurs if num is less than zero.

Pole error may occur if num is zero.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

- If the argument is ±0, -∞ is returned and FE_DIVBYZERO is raised.
- If the argument is 1, +0 is returned.
- If the argument is negative, NaN is returned and FE_INVALID is raised.
- If the argument is +∞, +∞ is returned.
- If the argument is NaN, NaN is returned.

### Notes

The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their argument num of integer type, std::log10(num) has the same effect as std::log10(static_cast<double>(num)).

### Example

Run this code

    #include <cerrno>
    #include <cfenv>
    #include <cmath>
    #include <cstring>
    #include <iostream>
    // #pragma STDC FENV_ACCESS ON

    int main()
    {
        std::cout << "log10(1000) = " << std::log10(1000) << '\n'
                  << "log10(0.001) = " << std::log10(0.001) << '\n'
                  << "base-5 logarithm of 125 = "
                  << std::log10(125) / std::log10(5) << '\n';

        // special values
        std::cout << "log10(1) = " << std::log10(1) << '\n'
                  << "log10(+Inf) = " << std::log10(INFINITY) << '\n';

        // error handling
        errno = 0;
        std::feclearexcept(FE_ALL_EXCEPT);

        std::cout << "log10(0) = " << std::log10(0) << '\n';

        if (errno == ERANGE)
            std::cout << "    errno == ERANGE: " << std::strerror(errno) << '\n';
        if (std::fetestexcept(FE_DIVBYZERO))
            std::cout << "    FE_DIVBYZERO raised\n";
    }

Possible output:

    log10(1000) = 3
    log10(0.001) = -3
    base-5 logarithm of 125 = 3
    log10(1) = 0
    log10(+Inf) = inf
    log10(0) = -inf
        errno == ERANGE: Numerical result out of range
        FE_DIVBYZERO raised

### See also

loglogflogl (C++11)(C++11) | computes natural (base e) logarithm (\({\small\ln{x}}\)ln(x)) (function)
log2log2flog2l (C++11)(C++11)(C++11) | base 2 logarithm of the given number (\({\small\log_{2}{x}}\)log2(x)) (function)
log1plog1pflog1pl (C++11)(C++11)(C++11) | natural logarithm (to base e) of 1 plus the given number (\({\small\ln{(1+x)}}\)ln(1+x)) (function)
log10(std::complex) | complex common logarithm with the branch cuts along the negative real axis (function template)
log10(std::valarray) | applies the function std::log10 to each element of valarray (function template)
C documentation for log10

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